Enhancement of the effectiveness of graphene as a transparent conductive electrode by AgNO₃doping

Single-layer graphene sheets have been synthesized by using chemical vapor deposition, and subsequently doped with AgNO₃at various doping concentrations (n_D) from 5 to 50 mM. Atomic force microscopy and field emission scanning electron microscopy images reveal the formation of ∼10-100 nm Ag particles on the graphene surface after doping. The type of n doping is confirmed by analyzing the n_D-dependent behaviors of Raman scattering and the work function of the doped graphene films. The sheet resistance monotonically decreases to ∼173 Ω/sq with the increase of n_Dto 50 mM, and the transmittance is reduced by only about 3% for the highest n_D. At n_D= 10 mM optimized doped graphene layers with a sheet resistance of 202 Ω/sq and a transmittance of 96% are obtained, resulting in a maximum DC conductivity/optical conductivity ratio (σ_DC/σ_OP) of ∼45.5, much larger than the minimum industry standard (σ_DC/σ_OP= ∼35) for transparent conductive electrodes.